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Old Nov 27, 2012, 07:48 AM
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Originally Posted by fredmdbud View Post
A melted solder joint is usually an indication of faulty soldering, either a dry joint (not enough solder) or a cold joint (insufficient flux and/or heat to allow the solder to fully melt and flow), resulting in an incomplete electrical/mechanical connection and a resistive joint. The solder joint should be smooth and shiny - if it's dull, it's advisable to apply flux and resolder.

Also, EC5's are rated to more than 120A continuous current. Using a single EC5 battery connector might insufficient - solder two EC5 connectors in parallel to the battery cables, and feed each ESC with its own EC5 connector.
Thanks for the info. Is there any indications that you can think of that can indicate a bad solder joint (other than smooth and shiny)? I.e. motor stutters or hesitates when you spool up to full throttle. I ask because this happens sometimes on my eurofighter and I'm not sure what is causing it. It seems to be random and doesnt necissarily happen at same throttle position all the time.
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Old Nov 27, 2012, 08:30 AM
RC is healthy for your brains!
Italy, Lombardy, Milan
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Hi everyone! I keep on getting directed towards the su 35 by all the good modellers here, so I am getting more persuaded into it.
I just read that the real one also does not have flaps, so my concern about them is much reduced.
Tell me something, if I implement the flaperons, would you say that you can manage the control properly provided that you also allow tailerons to be fully active during landing/takeoffs?
Would the tailerons deliver sufficient roll control in those moments? I would like to leave the wings dumb and inert, fully flapped out...
Is it one of those "Crazy Italian" suggestions?
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Old Nov 27, 2012, 08:35 AM
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Originally Posted by PeterVRC View Post
Not just one simplistic curved line....

Say in the case it does not 'match' that chart... then it creates a question of 'Why not in this case?". Maybe "Oh it is the area of it in proportion to the wing... or its rate of size change along its length". etc etc. Or what the prior wing profile is versus the new profile. Or how sharp the surface angle change occurs.
MANY things can totally change the 'chart' in this application. A 'generalisation' chart is half useless. Find out the FACTS yourself, in your application.

A generalization chart is half useless...
Simplistic curve lines...
Go tell an engineer!

Planes are BORN out of those charts.
Of course most of them are generalizations and idealizations of reality so maybe not 100% accurate but I can guarantee they predict really accurate in the range they have been calculated to apply.

And besides, unless you are taking actual MESURES by logging data of the response of the plane during flights, you will only get a feel of what the plane is doing. Those charts give you a better sense of what's happening. Of course it's very nice to experiment and see things yourself, I highly encourage that, but you are highly underestimating their potential.

For example, that CL-alpha curve for wings with and without flaps is meant to represent the outcome in lift of a wing at a certain FIXED SPEED in function of angle. That curve considers both "aerodynamic lift" and "angle of atac lift" And the only huge limitation is that after the wing stalls, predicitions using this model are erratic and non-reliable, so you see after exceeding some critic angle of atac lift decreases. This is usually fine for most aircraft but on thrust vectored jets you can keep control after wing stall, but then you are not only lifting with the wings but also with a component of thrust. But the most important thing here towards take offs is that the wings ALWAYS have a linear increment in lift vs angle of atac unless you exceed critical angle, something that does not happen on take off (Unless you do my cobra take off version ) and it also means that using LE flaps means you get LESS lift for the same angle but you get a new larger envelope of flight, with a later wing stall, and thus you can fly at greater angles of attack, and exceed the previous maximum lift. It makes physical sense because at high AoA the wing presnted a sharp edge and with the LE flap you are smoothing it out, letting the flow attach better to the surface and delaying stall. This will be the same pretty regardless of wing. What will change from one to another are just the coefficients. I can predict lots of things with those curves, just that you don't fully understand them doesn't mean they are worthless!
For example, the more chamber a wing has, means that curve cuts the Y axis in a higher mark, that means you have better coefficent of lift for a zero degree AoA. Instead, if you make a wing thicker, and the leading edge rounder, (As in 3D planes) you don't affect lift, but delay flow separation, which affects maximum CL, critical angle, ailerons responsiveness, etc. This will be seen in the graph as "longer curve", because you will reach critical AoA at later. With a thinner profile and sharper edge, the wing stalls earlier. You would see a shorter lline in the graph.
If instead, you are deploying flaps, that actually means MORE LIFT for the same angle of atack, but earlier stall, so they pretty work opposite of LE flaps.

There is actually a free software in which you can enter wing parameters and it calculates whatever curve you want. Search for XFLR5.

Just to make some reflection.





If you are further interested in learning, I suggest you get a copy on "Introduction to flight" from John D. Anderson. That's a pretty basic engineering literature, and it explains easily all this stuff.

Cheers!
Jandro.
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Old Nov 27, 2012, 08:40 AM
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Originally Posted by .Superfly. View Post
I just read that the real one also does not have flaps, so my concern about them is much reduced.
Tell me something, if I implement the flaperons, would you say that you can manage the control properly provided that you also allow tailerons to be fully active during landing/takeoffs?
Would the tailerons deliver sufficient roll control in those moments? I would like to leave the wings dumb and inert, fully flapped out...
Is it one of those "Crazy Italian" suggestions?
Someone told you wrong, the real Su-35s do have flaps.
I think the tailerons and thrust vectoring should be sufficient to provide roll control, but if you are not sure, just try it at a safe altitude until you get confident wih the aircraft response.

BTW, someone asked to compare the SU-35 with the Euro in high alpha terms.

The Eurofighter is more stable at high AoA than the SU is, but the later is more maneuverable.
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Old Nov 27, 2012, 08:49 AM
RC is healthy for your brains!
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http://www.sci.fi/~fta/Su-35.htm

I trusted that guy...
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Old Nov 27, 2012, 09:02 AM
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You misunderstood the guy, he says it USES flaperons! That's actually right!

In any case that must be a really old article since only the Su-35 Prototype featured canards.

Here you can see a production Su-35 landing with flaperons fully deployed:

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Old Nov 27, 2012, 09:25 AM
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Originally Posted by DamonH View Post
Thanks for the info. Is there any indications that you can think of that can indicate a bad solder joint (other than smooth and shiny)? I.e. motor stutters or hesitates when you spool up to full throttle. I ask because this happens sometimes on my eurofighter and I'm not sure what is causing it. It seems to be random and doesnt necissarily happen at same throttle position all the time.

like this...

Freewing stock fan stuter (0 min 5 sec)


Thats my stock eurofighter freewing fan. I first balanced it on 3s and when I ran it up with the stock ESC on 6S, it when up in flames when it made that sound.
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Old Nov 27, 2012, 09:32 AM
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Originally Posted by PAPE View Post
like this...

https://www.youtube.com/watch?v=_oNt...Y&feature=plcp

Thats my stock eurofighter freewing fan. I first balanced it on 3s and when I ran it up with the stock ESC on 6S, it when up in flames when it made that sound.
Yeah! Kinda like that...I just had a successful maiden Sunday and it made that sound when I throttled up after a landing pass that was too hot.
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Old Nov 27, 2012, 09:41 AM
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well that happens to mine too, I have no idea what it is.
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Old Nov 27, 2012, 10:22 AM
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I know that when the stuttering happens with Castle Creations ESCs, they recommend changing the ESC pwm. If anyone has info on how to program the stock ESCs, it would be most useful.
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Old Nov 27, 2012, 10:42 AM
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Originally Posted by PAPE View Post
like this...

https://www.youtube.com/watch?v=_oNt...Y&feature=plcp

Thats my stock eurofighter freewing fan. I first balanced it on 3s and when I ran it up with the stock ESC on 6S, it when up in flames when it made that sound.
Try changing the ESC timing. I had long conversations with Mark ExtremeRC over this and he said he encounters this on a regular basis during setup of the many he sends out the door. It varies and for him hes using the same batt/HobbyWing ESC for the wide range of motors.

It can happen for several reasons though. The ESC may not be able to process the pole count at a certain point, there can be an issue in the motor itself that isn't critical but the ESC senses and briefly stutters, solder joints etc.

My 2W25s and HobbyWings were doing this for some time till I tried adjusting the ESC timing. In the end I figured one motor was slightly off spec but once I increased the timing it rearly shows up. It still runs a little hotter than the other so I keep a close eye on it.
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Old Nov 27, 2012, 10:44 AM
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Quote:
Originally Posted by Whiskey Whiskey View Post
I know that when the stuttering happens with Castle Creations ESCs, they recommend changing the ESC pwm. If anyone has info on how to program the stock ESCs, it would be most useful.
On my stock esc. I never got to try difrent setings because it burnt on the first run up. But then i tried 8pwm 12pwm and al timings from 0- 25 and it never when away.
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Old Nov 27, 2012, 11:08 AM
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Originally Posted by Maxthrottle View Post
Try changing the ESC timing. I had long conversations with Mark ExtremeRC over this and he said he encounters this on a regular basis during setup of the many he sends out the door. It varies and for him hes using the same batt/HobbyWing ESC for the wide range of motors.

It can happen for several reasons though. The ESC may not be able to process the pole count at a certain point, there can be an issue in the motor itself that isn't critical but the ESC senses and briefly stutters, solder joints etc.

My 2W25s and HobbyWings were doing this for some time till I tried adjusting the ESC timing. In the end I figured one motor was slightly off spec but once I increased the timing it rearly shows up. It still runs a little hotter than the other so I keep a close eye on it.
This is great info. I thought i was the only one with this problem. The thing is i later tried a difrent motor. Hk 3025 outrunner. And the problem. Dint go away but got a little beter. But still did the same thing on the video. But with the hk motor I could here the motor start to go out of sync around 50-60% throttle.
I flew it like this any way but had to stop on the 3rd flight as the problem got worst and the motor cut of compleatly. 3 times.
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Old Nov 27, 2012, 11:11 AM
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Mine is the stock setup on my eurofighter as well...is there any instructions on programming stock euro esc?
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Old Nov 27, 2012, 11:26 AM
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Quote:
Originally Posted by SU-4ever View Post
A generalization chart is half useless...
Simplistic curve lines...Go tell an engineer! .......Cheers!
Jandro.
Thanks for jumping on that I was thinking weather I was going to explain or not.
I get the impression as some learn the particulars of flight dynamics they seem to get focused to specific parts and not the system as a whole. What known knowns that we have is the SU, Lockheed etc engineers aren't stupid and place these combinations to optimize results.

The SU-35 deploys the LE Flap at lower speeds not just for pure lift, but because of LO they no longer add saw tooths, fences or other remedies to clean flow over a buffeting wing and fuse flow. The combination of the flapperon with the LE flap is typical in most manuevers and help a very specific window of performance or issue particular to the design. Looking at a chart out of context means you may not be exploiting every available opportunity as they have engineered.

Because we fly our model LOS and pass through the little variations so quickly, we don't really notice the advantages just looking from a far because we're not in the plane. Look at a lot of the videos of the model with aft views. You can see many of the rudders being stressed from vortex flow as they twist from turbulent air. Its one of the reasons I gather why the LE Flaps extend into the LERX or fuse in line ahead of the rudder. Because they are forced to make things within min tolerances cause they can't just shove a longer heavier bolt to hold down the rudder they have to utilize other means to reduce stress to the frame. LE Flaps is just one of them.
For us and this model, my guess is LE flaps with work best for hard pitch changes and slow pre stall speeds with the flapperons with more alpha in the approach.

Superfly, I have both flapperons and tailerons. The tailerons with airflow and sufficient deflection are plenty roll responsive. With the TV even more so. On my second flight I deliberately kept the flapperons deployed at 50% for discovery. Ailerons input goes to minimums on the wings so roll isn't from them but was clearly sustained by the tailerons. I spent a few flight looking for the min thrust points and AoA profiles before stall to set up a landing throttle curve. It slows it down quite nicely but I ran out of flying season.
Since the model is already plenty manueverable with TV, I didn't try a 3D Elev>Flap mix yet.
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